1. Field of the Invention
The present invention relates to electrical and electronic circuits and systems. More specifically, the present invention relates to radar systems.
2. Description of the Related Art
See or Sense Through-the-wall (STTW) sensors and technologies are needed to satisfy current and future operational requirements for an enhanced capability to detect, locate, identify, and classify moving and stationary people or objects through walls, for clearing an urban facility in connection with military, police, security and/or commercial applications. The STTW sensor could be employed by soldiers or by robotic assets (air and ground) to provide detailed information on an occupied or unoccupied environment.
Prior approaches have involved impulse radar and swept frequency radar (CHIRP). Impulse radar transmits an ultra short pulse and can be processed with incoherent processing (detector) or coherent processing. The disadvantages of impulse radars are low average power and limited dynamic range. In addition coherent processing requires a tremendous processing load.
Swept frequency radar uses a mixing technique to convert range to frequency. This preserves an extremely high bandwidth (fine range resolution). Analog to digital bandwidth becomes range coverage and range resolution is the chirp frequency sweep bandwidth. Unfortunately high bandwidths require long frequency sweeps. This creates a minimum standoff range. To address this problem the linear frequency sweep is gated to create stepped frequency radar. One disadvantage of stepped frequency waveforms or any coded waveform is range sidelobes. Unfortunately, to discriminate small radar cross-sections that are close to large objects requires large dynamic range and low range sidelobes.
Finally, continuous wave radar systems have not proved effective for STTW applications. Hence, a need remains in the art for an improved radar for See Through the Wall applications.